1. Field of the Invention
The present invention relates to a liquid ejection apparatus and an ejection abnormality factor extraction method, and more particularly, to a liquid ejection apparatus which ejects liquid from a nozzle and an ejection abnormality factor extraction method which extracts a factor of an ejection abnormality.
2. Description of the Related Art
Inkjet recording apparatuses are known which comprise an inkjet head having a plurality of nozzles, and which record images onto a medium by ejecting ink toward the medium from the inkjet head.
In an inkjet recording apparatus, cases may occur in which the nozzles become blocked and it is impossible to eject ink droplets because of increase in the viscosity of the ink, infiltration of air bubbles into the inkjet head, adherence of paper dust to the ink ejection surface, and the like. If nozzle blockages of this kind arise, then dot defects occur in the image formed on the medium, thus causing degradation of the image quality.
In the related art, various types of liquid ejection apparatus having a device for determining ejection abnormalities have been proposed.
For example, Japanese Patent Application Publication No. 10-114074 discloses an ejection head comprising piezoelectric elements (electrostrictive vibrating elements) provided respectively in the ink flow channels for a plurality of nozzles, which ejects ink by applying a drive voltage to the piezoelectric elements, wherein an air bubble determination device is provided in order to detect the presence or absence of air bubbles in the ink flow channels by determining constantly, during printing, whether or not the voltage generated in the piezoelectric elements due to the volume change of the ink flow channels is an overvoltage which is not less than the drive voltage.
Moreover, Japanese Patent Application Publication No. 2004-276367 (in particular, FIGS. 16, 18, 19, and 22) discloses an apparatus comprising: an ejection head that ejects liquid inside pressure chambers (cavities) from nozzles by means of a diaphragm which can be displaced by driving actuators; and an ejection abnormality measuring device which determines the residual vibration of the diaphragm and determines ejection abnormalities due to adherence of paper dust to the vicinity of the nozzles of the head on the basis of the pattern of the residual vibration of the diaphragm thus determined. The ejection abnormality determination device comprises: a vibration determination device including an oscillation circuit which converts a variation in the electrostatic capacitance into a frequency, a frequency-voltage conversion circuit (F/V conversion circuit) which converts the frequency into a voltage; a residual waveform determination device having a waveform shaping circuit; a measurement device which measures the frequency and amplitude of the residual vibration waveform obtained by the residual waveform determination device; and a determination device which determines ejection abnormalities according to the measurement results from the measurement device.
However, in such liquid ejection apparatuses of the related art, there is a possibility that the circuit composition becomes complicated in a case where the liquid ejection apparatus is intended to extract various types of factors of ejection abnormalities, such as increased viscosity of the ink, the occurrence of air bubbles, adherence of dust such paper dust, and the like.
Japanese Patent Application Publication No. 10-114074 discloses a technology for determining whether the voltage generated in the driving piezoelectric element is the overvoltage which is not less than a drive voltage or not, in order to detect air bubbles. Thus determinable factors of the ejection abnormalities are limited to the presence of air bubbles only.
Japanese Patent Application Publication No. 2004-276367 discloses a technology in which the ejection abnormality determination device includes the oscillation circuit (for example, a CR oscillation circuit) which converts a electrostatic capacitance variation based on the residual vibration of the diaphragm into a frequency, the F/V conversion circuit which converts a frequency into a voltage, and the waveform shaping circuit. Therefore, the circuit composition is complicated and is generally expensive. Moreover, since ejection abnormalities are determined on the basis of the residual vibrations of the diaphragm, it is difficult to achieve highly accurate determination of ejection abnormalities.